In the data storage system manufacturing industry, various methods have been employed to minimize the detrimental influence of strong external rotational shock forces on the operation of the sensitive components comprising a direct access storage device (DASD). A typical DASD includes one or more data storage disks coaxially mounted on a hub of a spindle motor. The spindle motor rotates the disks at speeds typically on the order of several thousand revolutions-per-minute. Digital information is typically written to and read from the data storage disks by one or more magnetic transducer heads, or read/write heads, which are passed over the surfaces of the rotating data storage disks.
An actuator typically includes a plurality of outwardly extending actuator arms adapted to interleave one or more magnetic transducer heads mounted thereon into and out of the stack of data storage disks. During periods of DASD inactivity, the actuator is often restrained in a predetermined parked position by use of a passive locking or parking mechanism, such as a parking ramp apparatus, for example. The magnetic transducer heads are usually parked beyond the outer periphery of the data storage disks or over a dedicated portion of the disk surface, often termed a landing zone, situated away from the data storing portions of the disk.
Mishandling of either the DASD or a computer system into which the DASD is installed often results in displacement of the actuator from its parked position. Such direct and indirect mishandling often subjects the sensitive internal components of the DASD to significantly large rotational shock forces. The rotatably mounted actuator is generally susceptible to rotational forces and often rotates out of the parked position when the DASD is subjected to a sufficiently strong rotational shock force. Unrestrained movement of the actuator typically results in varying degrees of permanent damage to the sensitive surfaces of the data storage disks and to the magnetic transducers. A damaged region of the disk is generally unusable for subsequent storing of data. Also, any data stored at the damaged location may be irreparably lost.
Various methods and apparatus have been developed to reduce the potentially catastrophic results of unrestrained actuator rotation out of a preferred parked orientation during periods of DASD inactivity. In general, conventional latching mechanisms are designed to counteract detrimental actuator rotation within a limited range of acceleration. It is known in the art, for example, that commonly used inertial latching assemblies are generally effective for limiting unrestrained actuator rotation in the presence of high levels of externally induced actuator acceleration. It is also known in the art that commonly used magnetic or electromagnetic latch assemblies are generally effective for limiting such unrestrained actuator rotation in the presence of low levels of externally induced actuator acceleration.
A typical inertial latching assembly is designed to passively latch an actuator in a parked orientation until external rotational shock forces impinging the DASD are dissipated. Known inertial latches are typically mounted for rotation about a pivot axis in proximity to the actuator, and include a weighted portion and hook portion. In response to a sufficiently strong rotational shock force applied to the DASD, the hook portion of the inertial latch typically rotates about the pivot axis and engages a receiving hook or other capturing member protruding from the actuator. A biasing mechanism is generally employed to return the inertial latch to its original, non-engaged orientation after the external shock forces are dissipated.
Inertial latching mechanism are generally effective only at relatively high levels of externally induced actuator acceleration. Elevated levels of actuator acceleration must generally be present in order to overcome the force produced by the biasing mechanism required to maintain the inertial latching mechanism in its non-engaged orientation. Low to moderate levels of induced actuator accelerations are therefore not generally addressed when designing a conventional inertial latching mechanism.
In contrast, magnetic or electromagnetic latching mechanisms are generally effective only at relatively low levels of externally induced actuator rotational acceleration. In accordance with a conventional magnetic-type latching device, a magnetic coupling force of limited range is generally produced between the latching device and the actuator to restrain the actuator in an engaged or latched orientation. It is generally considered impractical to employ a magnetic-type latching device to counteract relatively high levels of externally induced actuator rotational acceleration. The intensity of the magnetic coupling force required to satisfactorily restrain a rotatable actuator in the presence of such high acceleration levels would typically require application of an excessively large force to free the actuator from the magnetic latch prior to initiating normal operation, and would likely interfere with the efficient operation of the actuator voice coil motor and other DASD operations. Also, electromagnetic latching mechanisms that employ a solenoid would require delivery of an appreciable amount of current to the solenoid in order to de-couple the latching device from the actuator. Such solenoids would generally be significantly larger than solenoids used in low-acceleration type electromagnetic latches, and would typically occupy an unacceptable amount of space within the relatively compact housing configurations of present and future small form factor DASDs.
A trend has developed in the DASD manufacturing community to miniaturize the chassis or housing of a DASD to a size suitable for incorporation into miniature personal computers, such as lap-top and hand-held computers, for example. Various industry standards have emerged that specify the external housing dimensions of small and very small form factor DASDs. One such recognized family of industry standards is the PCMCIA (Personal Computer Memory Card Industry Association) family of standards, which specifies both the dimensions for the DASD housing and the protocol for communicating control and data signals between the DASD and a host computer system coupled thereto. Recently, four families or types of PCMCIA device specifications have emerged. By way of example, a Type-I PCMCIA DASD must be fully contained within a housing having a maximum height dimension of 3.3 millimeters (mm). By way of further example, a Type-II PCMCIA device housing must not exceed a maximum height of 5.0 mm in accordance with the PCMCIA specification. A maximum height of 10.5 mm is specified for the housing of Type-III PCMCIA devices, and Type-IV devices are characterized as having a maximum housing height dimension in excess of 10.5 mm.
It is anticipated that the industry trend of continued miniaturization of DASDs will eventually result in the production of systems complying with the Type-II PCMCIA specification. Such Type-II PCMCIA DASDs will likely have external housing dimensions of approximately 54 mm.times.86 mm.times.5 mm, and include a data storage disk having a diameter of approximately 45 mm and a width dimension similar to that of a standard credit card. It will likely be highly desirable to employ an effective actuator latching assembly within such small and very small form factor DASDs, such as Type-II PCMCIA DASDs. Those skilled in the art, however, will appreciate the difficulties associated with employing an effective latching mechanism suitable for use within these very small form factor DASDs. The maximum allowable housing dimensions imposed by the Type-II PCMCIA specification, for example, necessarily results in a highly compact packaging configuration within the DASD housing, with minimal clearance and tolerances afforded between adjacent components.
Employment of prior art latching mechanisms within the compact environment of a small form factor DASD is generally considered problematic for a variety of reasons. A conventional inertial or magnetic-type latching mechanism generally occupies an appreciable amount of space within the compact DASD housing. More significantly, a conventional inertial or magnetic-type latching mechanism is generally effective within a relatively narrow range of externally induced actuator acceleration levels, thus rendering the actuator and other sensitive components of the DASD vulnerable to detrimental levels of induced acceleration outside the prescribed range. These and other characteristics of prior art actuator latching mechanisms generally represent significant limitations in the development and optimization of highly reliable, portable DASDs.
There exists within the DASD manufacturing community a need to provide effective protection against unrestrained actuator movement in the presence of a broad range of externally induced acceleration levels in order to minimize potential damage to the sensitive internal components of standard and miniaturized DASDs. There exists a further desire to incorporate the advantageous attributes of inertial and magnetic-type latching mechanisms within the compact packaging configurations of small and very small form factor DASDs. The present invention fulfills these and other needs.